Refrigerant expansion valve



Nov. 18, 1969 N KE ET AL 3,478,774

REFRIGERANT EXPANSION VALVE Filed May 24. 1968 55 $3 70 I126 40 M a /8- if: 5;; -|IllIllllllfillllllllllllllk ,4 EVAPORATOR 41 v 38 Z 45 42 V CONDENSER COMPRESSOR INVENTORS THaMAs E. Nonxea United States Patent Office 3,478,774. Patented Nov. 18, 1969 US. Cl. 137-4545 5 Claims ABSTRACT OF THE DISCLOSURE This invention proposes a refrigerant expansion valve wherein the valve casing is permanently soldered or otherwise connected into the refrigerant system, as for example directly to the evaporator. The flow control and thermostatic actuator components are formed as a capsule separate from the valve casing, thereby permitting low cost factory fabrication of the system, followed by in-the-field installation of the capsule, as necessary for initial installation or replacement operation.

The removable capsule preferably has screw thread attachment to the valve casing, thereby permitting easy connection or detachment without special tools. Factory superheat calibration is facilitated by a screw driver rotation of the valve element which effects axial movement of a superheat spring seat or nut element.

THE DRAWINGS The single figure is a sectional view through one embodiment of the invention showing schematically its location in a refrigerant system.

The system comprises a conventional compressor 10, conventional condenser 12, the invention expansion valve 14, and conventional refrigerant evaporator 16 connected in a closed circuit or loop. Capacity or size of the components is of course determined by the system cooling requirements. For example automobile air conditioning would require less cooling capacity than room conditioning, thus requiring a differently sized and proportioned valve 14 in each case. The illustrated valve 14 comprises a hydro-formed metallic casing 18 of cup-like character having a liquid refrigerant inlet opening 20, and a vaporous refrigerant outlet opening 22. Removably disposed within this casing is a capsule 24 which includes a plastic plug-like valve body 26 and a metallic shell-diaphragm assembly 28. The capsule has no permanent or destroyable connection with casing 18; therefore the casing can be factory soldered or brazed directly to evaporator 16 while the capsule is not yet inserted into the casing. The capsule power element is thus not subject to destruction by heat.

Valve body 26 is formed with a refrigerant flow pass age which comprises a first cylindrical axial passage 32 and a connecting cross passage 34; the peripheral side surface of the plug is recessed, as at 36, so that refrigerant can flow freely in both arrowed directions through passage 34 as it seeks the outlet opening 22.'A first annular O-ring seal 38 confines all of the refrigerant flow to passage 32; i.e. no fluid leaks between the plug 26-casing 18 joint. A second annular O-ring seal 40 prevents refrigerant flow into the casing space above passage 34.

The illustrated valve is an externally equalized construction having an equalizer tube 41 extending from the casing 18 to the system suction line 43. An internally equalized structure would be built without seal 40 and equalizer tube 41.

Metering of refrigerant through passage 32 is accomplished by a cylindrical valve element 42 having a spherical surface registering with the seat at the passage 32 entrance. As shown, element 42 is connected with a stem 44, either by being machined as an integral structure or by welding. Stem 44 extends upwardly through plug body 26 into pressure contact with a pad 46 carried by metallic diaphragm 48. The diaphragm can be of bellows character if desired. Diaphragm 48 is sandwiched between two shallow dish-like shell elements 50 and 52, the three member assembly then being permanently connected together by a continuous peripheral weld 54 to form the aforementioned assembly 28.

Shell element 50 is provided with a sleeve-like extension 51 which telescopes over the upper end portion of plastic plug 26. Permanent connection of the sleeve extension to the plug may be accomplished by forming the plug with one or more recesses or indentations 53, and then staking parts of the metallic extension into these indentations. Indentation 53 can be an endless groove if desired.

The plug 26-shell 28 assembly forms the aforementioned removable capsule 24. As shown, the sleeve portion 51 of this capsule is externally threaded to mesh with threads preformed in the upper mouth portion of metallic casing 18. Before threading the capsule down into the casing an O-ring seal 55 may be positioned around the sleeve 51 above its threaded area. When the capsule is fully threaded into casing 18 the seal 55 is squeezed against the preformed flaring wall portion 57 at the casing mouth area, thus sealing the casing 18 interior from the ambient atmosphere.

As schematically shown in-the drawing, upper shell element 52 mounts one end of a capillary tube 58 which is of suflicient length to position a connected bulb 60 in the thermal contact with the system suction line 62. Refrigerant vaporized in evaporator 16 produces a superheat condition in the suction line, this condition being reflected in a heating of the bulb 60 charge (which is usually the same substance as the system refrigerant), an increase in the pressure above diaphragm 48, and a downward motion of the stem 44 and valve element 42. The downward opening movement of element 42 increases the refrigerant flow through evaporator 16, and this is reflected in a lessened superheat in the suction line; the bulb 60 temperature then drops to reduce the pressure above diaphragm 48 and effect an upward closing movement of valve element 42. The general aim is to control or meter the refrigerant fiow through the evaporator to produce a substantially constant superheat in spite of fluctuations in evaporator cooling load.

The value or setting of the superheat is controlled by a compression spring 62 which has its lower end seated against a seat formed by recess 64 in plug body 26. The upper end of the spring seats against a nut 66 which is threaded onto threads cut into stem 44. During service nut 66 acts as an integral part of stem 44 so that the spring force acts upwardly on the nut against the opposing force produced by the gas pressure above diaphragm 48. The adjusted position of nut 66 on stem 44 determines the spring force and consequently the superheat setting.

Calibration of the superheat setting is performed prior to installation of the capsule 24 into casing 18. The process may merely involve connection of the capsule inlet section to an air pressure source and measuring the air flow while bulb 60 is held at the desired temperature setting. Valve element 42 is provided with a screw driver slot 68 so that the valve element and its connected stem 44 can be turned to adjust the axial position of nut 66 on the stem. The calibration fixture (not shown) must be equipped with a turnable fixture keyed to slot 68 so that the calibration process can be carried out without destroying the seal around valve body 26. Stem 44 can turn relative to nut 66 because the frictional force pro- 3 vided by the contact area and moment arm at the spring 62-nut 66 connection point is greater than that at the nut threads; thus ordinarily no positive anti-rotation means would be needed between nut 66 and plug body 26.

During the calibration process the air fiow through passage 32 may be noted and element 42 turned until the desired flow is achieved. Then adhesive may be applied at the nut 55-stern 44 point to preserve the calibration. An access opening 70 is preformed in the plug 26 side wall to apply the adhesive; without opening 70 to the stern 44-nut 55 joint would be inaccessible.

The drawings show the valve arranged with opening 20 as the inlet and opening 22 as the outlet. It will be understood however that the valve can be arranged so that opening 22 is the inlet and opening 20 is the outlet.

A feature of this invention is the simplicity of the capsule 24 construction, especially the superheat adjustment which consists only of a slot 68, spring 62 and nut 66. The simple nature of this adjustment eliminates component parts, and because of that fact also permits some size reduction in the existing parts, for example the length and diameter of plug 26 and casing 18. This size reduction is achievable without reducing the power or force characteristic of power element 28 because the element is located outside of casing 18; thus the power element diaphragm can have a relatively large area for satisfactory force development while still using a small diameter casing 18.

We claim:

1. A cartridge type refrigerant expansion valve comprising a cup-like casing having an open mouth, a liquid refrigerant inlet opening in a first wall portion of the casing, and a second vaporous refrigerant outlet opening in a second wall portion of the casing; a valve body plug removably disposed within the casing; thermostatic power element actuator means comprising a shell-diaphragm assembly carried by the valve body plug outwardly of the casing mouth; the end area of the plug remote from the shell-diaphragm assembly having flow passage means therethrough furnishing communication between the aforementioned inlet and outlet openings; a valve element located within the casing beyond said remote end of the plug for movement toward and away from the flow passage means to control refrigerant flow therethrough; a stem connected with the valve element and extending through the valve plug into operable engagement with the aforementioned diaphragm whereby movement of the diaphragm produces a corresponding movement of the stem and valve element; threads formed on the stem in the area thereof adjacent the diaphragm; a first spring seat comprising a nut threaded onto the threaded portion of the stem; at second spring seat formed by a recess in an end of the plug; superheat spring means comprising a compression spring trained between the first and second spring seats; and means for moving the nut along the stem comprising a tool-engageable surface formed on the valve element; said stem being free to turn relative to the diaphragm so that a turning force applied to the valve element produces an axial motion of the nut for superheat adjustment.

'2. The expansion valve of claim 1 wherein the shell of the aforementioned shell-diaphragm assembly is provided with an extension sleeve telescoping onto the valve body plug; said sleeve having threads meshing with threads formed on the interior surface of the casing, whereby to lock the shell-diaphragm assembly to the casing.

3. The expansion valve of claim 2 wherein a portion of the sleeve is staked into at least one depression in the plug to lock the shell and plug together.

4. The expansion valve of claim 1 wherein the mouth of the cup-like casing is defined by an annular flaring wall portion; the shell of the aforementioned shelldiaphragm assembly having an extension sleeve telescoping onto the valve body plug; said sleeve extending through the mouth of the casing into the casing interior; the combination further comprising a compressible sealing element squeezed between the aforementioned flaring wall portion and the shell-sleeve juncture area.

5. The expansion valve of claim 1 wherein the plug is provided with an access passage extending from its ex terior side surface into the aforementioned recess, said access passage permitting the application of adhesive to the joint between the nut and stem.

References Cited UNITED STATES PATENTS 1,945,834 2/1934 Terry. 2,250,362 7/1941 Dube. 2,594,701 4/1952 Wolf.

ARNOLD ROSENTHAL, Primary Examiner US. Cl. X.R. 25 l61.4, 176 

